Various embodiments of implements for deeply loosening soil are known. They have blades that are mounted in an adjustable blade holder and pivot up and down within a plane paralleling the progress of the vehicle, forced against a stop by a spring. The stop ensures that each blade before entering the soil will assume a specific angle that at least approximates the angle the force is applied at. The blade enters the soil as the vehicle progresses. The soil forces the blade to pivot, but not enough to break up the ground when retracted. The slight shifting of the blade in the soil out of the angle established by the stop lifts the blade against the force of the spring. Once free of the soil, the blade will be pivoted back again by the spring into its disengaged position against the stop. The blade or a row of blades is engaged in a known manner by a crank that rotates as the vehicle progresses to an extent that establishes how far the blade will enter the soil. An implement of this genus is known from U.S. Pat. No. 3,204,703 for example.
European Patent discloses a parallel position of the blade over a total cycle of motion, allowing the blade's penetration to be adjusted just by raising and lowering a frame in relation to a support, a roller, that rests on the ground. The stop can also be adjusted independently to vary the angle of the blade to the ground in order to control how the soil is loosened.